The present invention relates to a copier of the type having an intermediate tray.
A conventional copier of the type disclosed in, for example, Japanese Patent Laid-Open Publication (Kokai) No. 61140/1986 and Japanese Utility Model Laid-Open Publication No. 128566/1988 has a body for reproducing a document laid on a glass platen on a paper sheet, paper selecting means for selecting paper sheets, magnification changing means for changing a magnification of the body, and reporting means for reporting the operator of a condition wherein a copying operation would be effected more effectively if the document on the glass platen were changed in position with respect to the longitudinal and lateral directions. Let this type of copier be referred to as Type I copier. Another conventional copier, or Type II copier, has a body for feeding paper sheets from a paper feed device to a register position and reproducing a document laid on a glass platen on a particular number of paper sheets from the register position entered on an operating section, paper selecting means for selecting the paper sheets, magnification setting means for setting a magnification of the body, and an intermediate tray for stacking paper sheets each carrying an image formed by the body on one side thereof and refeeding them to a register position to form images on the other side. Still another conventional copier, or TYPE III copier, is disclosed in Japanese Patent Laid-Open Publication No. 106132/1978 and constructed to sense a document size prior to a copying operation, determine a necessary paper size on the basis of the document size and a magnification, and automatically select, if paper sheets of the determined size exist in a paper feed section, such paper sheets or, if otherwise, interrupt or end the copying procedure.
A further conventional copier, or Type IV copier, assigns to each copy mode a particular paper transport path and a particular position where a paper sheet waits (or is accommodated in an intermediate tray). Specifically, (1) in a composite or combination copy mode, a paper sheet is directly transported to a register position. (2) In a two-sided copy mode effected with a single paper sheet, the paper sheet carrying an image on one side thereof is turned over by a turning section, transported to the register position, and then fed from the register position to form an image on the other side thereof. (3) In a two-sided copy mode effected with a plurality of paper sheets, the paper sheets are sequentially stacked on an intermediate tray included in the turning section and without being steered to the register position. In an interrupt copy mode for effecting interrupt copying while a composite mode or a two-sided copy mode operation is under way, the copying operation under way is interrupted and then resumed after another copying operation has been executed. In the above modes (1) and (2), since a paper sheet exists at the register position at the end of the first copying operation, an image cannot be reproduced on another paper sheet. In these modes, therefore, after the first copying operation, the interrupt copy mode is inhibited so long as the paper sheet exists at the register position.
The problem with the Type II copier described above is that in the two-sided copy mode the set or desired number of copies should not be greater than the number of paper sheets accommodatable in intermediate tray. Hence, when the number of paper sheets accommodatable in the intermediate tray changes with the size or orientation of a document, e.g., when the document is laid on the glass platen in a different position with respect to the longitudinal and lateral directions as in the Type I copier, the set number of copies has sometimes to be changed in matching relation to the number of paper sheets accommodatable in the tray. If the set number of copies were not changed, the actual number of copies produced by the copier would be short of the set number of copies, or more than the number of paper sheets accommodatable in the intermediate tray would be received in the tray. The Type III copier also has to limit the set or desired number of copies to the number of paper sheets accommodatable in the intermediate tray or less. However, when the number of paper sheets accommodatable in the intermediate tray changes with the paper size, the Type III copier does not allow the operator to enter a desired number of copies since which paper size is selected is not known until the document size has been sensed.
In the light of the above, two different approaches have heretofore been proposed, i.e., one which limits the maximum set number of copies to the number of paper sheets particular to a paper size which would minimize the number of paper sheets accommodatable in the intermediate tray, and one which reproduces only the same number of copies as the number of paper sheets accommodatable in the intermediate tray by ignoring the set number of copies. However, the former approach is disadvantageous in that even when the paper size allows a greater number of paper sheets to be received in the intermediate tray, the productivity of copies is low. The problem with the latter approach is that the user is apt to overlook the fact that the number of copies actually produced is short of the set number of copies.
Further, the Type IV copier inhibits the interrupt copy mode every time the first copying operation ends and so far as a paper sheet exists at the register position. This often prevents the interrupt copy mode from being executed depending on the desired copy mode and the desired number of copies, also lowering the productivity and, in addition, confusing the operator.